why // is needed

[Jeff Kingston]

It is a general rule in Lout that when two objects are separated
only by white space, they come out side by side.  Thus if you
type

    @Document

followed by

    @Text @Begin ... @End @Text

these two objects are placed side by side in the output by Lout.
This is a disaster because it means that @Document's multiple
pages are placed beside another thing and hence get lumped
together into one page of PostScript output.

The // symbol is from raw Lout, and it means to place the
object following it vertically below the object preceding
it.  This allows the pages of @Document to be at the top
level and so to be recognized as separate things to be
placed on separate PostScript pages.

Jeff